This invention relates generally to tool holders with resharpenable cutting tool inserts. More particularly, it relates to an improved quick-change holder for a resharpenable form tool insert.
Machine tools such as screw machines, turret lathes, CNC lathes and the like use various types of tools held in tool holders to remove material from a rotating workpiece. One common tool type is a resharpenable form tool with a integral dovetail, which is periodically resharpened on its top planar surface and repositioned in the dovetail slot. This type of tool can cause substantial downtime due to the need to relocate the resharpened planar surface on the horizontal center line of the rotating workpiece, so that the tool cutting edge addresses the workpiece at the proper top rake angle and front clearance angle.
Another type of form tool in common use employs a thin throwaway carbide insert, which is discarded after it becomes dull. The carbide insert is clamped from the top upon a tool support. Due to the need to support the thin insert, the tool support must often be especially configured with a profile corresponding to the form profile of the carbide insert, thereby adding to the expense of the form tool.
It would be desirable to provide a tool holder for a form tool which provides the economies of a resharpenable form tool without the accompanying delay and expense due to downtime required to reposition the tool after sharpening. It would also be desirable to provide a tool holder for a removable insert which is universal for a variety of insert shapes and sizes without requiring especially profiled supports for the tool inserts.
In order to quickly change a resharpenable tool insert, the tool holder must be adapted to relocate the resharpened insert quickly and efficiently in a consistent manner. There must also be means to securely and safely hold the tool insert to prevent slippage, breakage or chatter while it is removing material from the workpiece. Several varieties of quick change tool holders directed toward this end have been disclosed in the prior art. Exemplary of these are U.S. Pat. No. 2,241,024 issued May 6, 1941 to G. Wahnish, which employs different thickness compensation members to compensate for variation in the thickness of cutoff tools.
A resharpenable cutoff tool and holder, in which the cutoff tool is repositioned and clamped by means of a sliding adjustable wedge member is shown in U.S. Pat. No. 2,390,653 issued Dec. 11, 1945 to Kilgore.
Another type tool holder utilizing a sliding wedge secured by a draw-bolt is disclosed in U.S. Pat. No. 2,275,326 issued Mar. 3, 1942 to Severson and U.S. Pat. No. 2,488,172 issued Nov. 15, 1949 to Catlin, et al. The latter two patents clamp a tool bit against an overhanging shelf in the tool holder and support the resharpenable tool bit on a slidable wedge-shaped member. The location of the cutting edge of the resharpened tool changes after resharpening, even though it is replaced in the identical position in the tool holder.
Accordingly, one object of the present invention is to provide an improved resharpenable form tool and tool holder adapted for resharpening and quick replacement of the form tool.
Another object of the invention is to provide an improved universal quick change tool holder for a resharpenable insert which does not require resetting the tool holder with respect to the workpiece after resharpening.
Still another object of the invention is to provide an improved form tool holder for accurately locating a resharpenable insert at the same cutting position laterally, horizontally and vertically after resharpening.